RESUSCITATION TIME LIMITS IN EXPERIMENTAL PULSELESS ELECTRICAL-ACTIVITY CARDIAC-ARREST USING CARDIOPULMONARY BYPASS

Study objective: The objective of this study was to determine the time limits of resuscitation following increasing intervals of untreated p ulseless electrical activity using cardiopulmonary bypass as the resus citation tool. Design: Prospective controlled laboratory investigation using a canine model of pulseless electrical activity. Subjects: 20 m echanically ventilated mongrel dogs of either sex under Halothane anes thesia. Interventions: Pulseless electrical activity was produced by c lamping the endotracheal tube. The ECG and hemodynamics were monitored until loss of pressure fluctuations by aortic catheter. Animals were then randomized to remain in untreated pulseless electrical activity f or 10 min (Group I), 15 min (Group II) or 20 min (Group III). Followin g each interval, resuscitation was begun using fixed-flow closed-chest cardiopulmonary bypass (50 ml/kg/min) and an epinephrine infusion (4 mug/kg/min). Cardiopulmonary bypass was continued for 30 min or until return of spontaneous circulation. Following return of spontaneous cir culation, animals were weaned from bypass and observed for 1 h. Measur ements and main results: Return of spontaneous circulation was achieve d in 100% (7/7) Group I, 50% (3/6) Group II and 29% (2/7) Group III an imals (P less-than-or-equal-to 0.02, Group I vs. Group Ill). One-hour survival was achieved in 71% (5/7) Group I, 33% (1/3) Group II and 0% (0/2) Group III animals (P > 0.05). Coronary perfusion pressure, bypas s flow and arterial blood gases during reperfusion were similar betwee n groups. Conclusion: Cardiopulmonary bypass is effective at restoring spontaneous circulation when used early in asphyxial pulseless electr ical activity cardiac arrest. Cardiopulmonary bypass is less effective when used after 15 min of pulseless electrical activity with no survi vors following 20 min of arrest.